The present invention relates to a start controller for an engine of a vehicle.
In a conventional vehicle, a switch contact of a key cylinder is connected to a power line from an automotive battery. The switch contact is mainly operated to turn ON/OFF of an ignition circuit, locked and operated by a key intrinsic for the cylinder, and inhibited to start an engine by a third party who has no such key.
FIG. 8 shows an electric circuit diagram of an example of an ignition circuit of a conventional vehicle. This ignition circuit is of a contact point type used for a 4-cylinder engine.
The ignition circuit will be described by referring to FIG. 8. Reference numeral 101 designates an automotive battery, 102 an ignition coil, 105 a distributor, 113 a cylinder head (in an engine), and 210 an ignition key cylinder. A section surrounded by two-dotted chain line 100 is disposed in an engine room, and a section surrounded by two-dotted chain line 200 is installed in a driver's cab.
The negative terminal of the battery 101 is connected to an automotive body (a body earth), and the positive terminal is connected to a power line La. The power line La supplies a positive voltage to the sections of the vehicle, and the switch contact of the ignition key cylinder 210 in the driver's cab is connected to the line La. In other words, the line La is branched to the terminal of the contact B of the cylinder 201 and the terminal of the contact IG.
The key cylinder 201 is a rotary switch, which becomes rotatably when the key 202 intrinsic for the cylinder is inserted. When the cylinder 201 is rotated, the contact B and the contact IG are closed to connect the power line (i.e., the engine switch is closed), and the power is supplied to a primary coil 103 and other circuits (e.g., a fail-cut valve).
The other end of the coil 103 is connected to the breaker arm 107 of the distributor 105. The distributor 105 has a rotary head 112 including a rotor 110 and segments 111a to 111d, and a breaker plate including a cam 106, a breaker arm 107 and a point arm 108. The rotor 110 and the cam 106 are coupled to the same drive shaft (not shown), which is connected to the crankshaft of the engine to rotate as the engine rotates.
Reference character C designates a spark preventing capacitor of the contact point due to a chattering.
When the contact point composed of the contacts of the breaker arm 107 and the point arm 108 is closed, a primary current is flowed in a closed circuit consisting of the positive terminal of the battery 101, the ignition key cylinder 201 (contacts B to IC), the primary coil 103, the breaker arm 107, the point arm 108 and the body earth when the engine switch is ON (the ignition circuit is closed), and the primary coil generates a magnetic flux. When the arm 107 is lifted by the rotation of the cam 106 to open the contact point in this state, the primary current is interrupted to abruptly reduce the magnetic flux generated in the coil 103. Since the primary coil 103 and the secondary coil 104 are magnetically coupled, the secondary coil 104 induces a high voltage due to the abrupt change of the magnetic flux. The high voltage induced in the secondary coil 104 is applied to the rotor 110, which distributes the high voltage to the segments 11a to 11d at a predetermined timing. The spark plugs 114a to 114d of the cylinder head 113 are respectively connected to the segments 111a to 111d thereby to generate spark discharge when the high voltage is applied.
More specifically, in the vehicle of this type, the start of the engine is controlled by the ON/OFF of the power line, the engine is locked in the state that the primary current (in the primary coil) of the ignition coil is interrupted to prevent the spark voltage from generating (in the secondary coil), thereby inhibiting the start of the engine.
In the conventional vehicle of this type, the ON/OFF contact of the power line for controlling the start of the engine is provided only in the ignition key cylinder. However, the power line connected to the key cylinder is connected to the terminal of the contact B and the terminal of the contact IG on the back of the ignition key cylinder (at opposite side of an key plug-in opening), and can be readily led out. Thus, even if there is no key intrinsic for the vehicle, when the cord is removed and connected, the power line can be connected to apply the voltage of the automotive battery to the ignition circuit and the other circuits equivalent to the closed engine switch.
Therefore, the engine is heretofore started by connecting the ignition circuit to the battery by a third party who have no key intrinsic for the vehicle, and the vehicle might be thus stolen.